Heat exchanger



April 6, 1965 w. F. ANDERSON ETAL 3,176,761

HEAT EXCHANGER Filed 001;. 29, 1962 WILLIAM F. ANDERSON BY DONALD F. CASEY IN VEN TORS ATTORN EY United States Patent 3,176,761 HEAT EXCHANGER William F. Anderson, Canoga Park, and Donald F. Casey, Granada Hills, Califl, assignors to North American Aviation, Inc.

Filed Oct. 29, 1962, Ser. No. 233,593 1 Claim. (Cl. 165-81) The present invention relates to heat exchangers and more particularly to vapor generators wherein the transfer of heat is effected between a fluid such as molten sodium at a relatively low pressure and another fluid such as steam at supercritical temperatures and pressures.

In a shell and tube heat exchanger wherein one fluid flows through a chamber defined by spaced tube sheets or headers which support the opposite ends of tubes through which another fluid flows, the point at which leakage is most likely to occur is along the adjacent surfaces of the tube sheet or header. In liquid sodium-water heat exchangers even minute leakage at this point results in rapid corrosion within the cracks and crevices between the tube and the tube sheet or header formed during the rolling or Welding together of these two elements.

It is therefore an object of the present invention to provide an improved heat exchanger wherein the possibility of corrosive action at the junction of the tube sheet or header and the tube bundle is substantially reduced.

Another object of the present invention is to provide an improved tube sheet or header structure which is capable of withstanding large pressure differentials and has improved tube connecting members.

It is another object of the present invention to provide a steam generator module utilizing a liquid metal as a primary fluid which is simple in construction and will Withstand the temperature and pressure gradients required for supercritical steam generation.

Another object of the present invention is to provide a header for a steam generator of improved integrity which substantially eliminates corrosion-promoting crevices.

A further object of the present invention is to provide a modular heat exchanger for enerating supercritical steam utilizing a liquid metal primary fluid which is simple in construction and reduces the probability of tube failure.

These and other objects and advantages of the present invention will be more apparent from the following description and the drawings, made a part hereof, in which:

FIG. 1 is a partially sectioned side View of the heat exchanger of the present invention; and

FIG. 2 is one quadrant of a section along the line 2-2 of FIG. 1.

Referring to FIG. 1 in detail, the heat exchanger of the present invention is shown and described for illustrative purposes as employing a liquid sodium primary fluid utilized for the generation of supercritical steam. However, it is understood that other primary and secondary fluids may be employed for the generation of high pressure vapor. The heat exchanger of the preferred embodiment comprises a cylindrical shell member having a primary fluid inlet 12 and primary fluid outlet 14, outlet and inlet headers 16 and 18 respectively, and a plurality of secondary fluid tubes 20 interconnecting the headers 16 and 18. These tubes 20 may be fabricated from ferritic or austenitic steel depending upon temperature service. The shell 10 may be provided with a bellows 22 to compensate for differential expansion between the shell 10 and the tube bundle 2%, if necessary. The headers 16 and 18, which may be identical in structure, are preferably constructed of an outer section 24 and an inner tube sheet section 26. The tube sheet 26 has an inner spherical sur- 3,176,761 Patented Apr. 6, 1965 face 28 and a plurality of outer bosses through which ports 30 have been bored, thereby forming a plurality of cylindrical or tubular extensions 32. The ports 30 terminate at one end with the tubular extension 32 and at the other end at the spherical surface 28. The ports 30 are preferably parallel to each other and to the longitudinal axis 34 of the tube sheet section 26. An outer circumscribing tubular extension 36 having the same diameter as the shell 10 is also provided on the outer surface of the tube sheet section 26 so that the shell 10 may be welded directly to the extension 36.

As an example, the tube sheet section is forged 6 inches in diameter with 37 bosses upset on the flat (liquid metal) side. These bosses are bored out to form tubular extensions 32 to which the tubes 20 are welded using insideout welding techniques well known in the art. The shell 10 is then Welded to the circumscribing extension 36. This type of tube sheet attachment eliminates the crevice formed in the rolled or welded joint employed in the prior art and the requirement for inert gas blankets adjacent the tube sheet. In this manner the tube sheets employ a generally spherical shape, thereby providing inherently strong structural shape, minimum surface-to-volume ratio, but do not require the penetration of the tube bundle into the tube sheet.

At longitudinally spaced intervals baflles or supports, not shown, may be provided to promote heat exchanging engagement and mixing of the primary fluid. Stagnating baffles at the high temperature end of the heat exchanger may also be utilized to minimize thermal shock in the event of feedwater loss. The modular heat exchangers of the present invention are preferably mounted vertically in order to promote adequate circulation of the supercritical fluid upward within the tubes 20 and to encourage proper circulation of sodium down through the shell. The use of hydrogen detectors, rupture discs, and vent pipes, as well as other modifications and additions to the basic combination of the present invention will be recognized by those skilled in the art. Therefore, the present invention is not limited by the foregoing specific description but only by the appended claim.

We claim:

A heat exchanger comprising:

(a) a tubular shell having spaced inlet and outlet ports,

(b) a bundle of tubes extending in generally parallel relation to and within said shell,

(c) means associated with said shell for compensating for differential thermal expansion between said shell and said tube bundle,

(at) at least first and second headers suitably positioned in a spaced apart relationship by said. tube shell and said tube bundle,

(e) each of said headers comprising:

(1) an inner tube sheet member,

(2) an outer member integrally attached to said inner member,

(3) said attached inner and outer members having a longitudinal axis,

(4) a truncated cone in said outer member defining an inner passage concentrically positioned about said axis,

(5) respective wall portions in said inner member defining a substantially flat outer surface and a hemispherical inner surface cooperating with the base of said truncated cone passage,

(6) said inner truncated cone and said inner hemispherical surface defining an internal volume in said attached inner and outer members,

3 (7) a plurality of spaced apart ports in said inner hemispherical surface extending through said inner hemispherical surface to said flat outer surface in a direction substantially parallel with said axis, and (8) a plurality of tubular extensions integrally formed on said flat outer surface, (9) each of said tubular extensions defining one end of each of said ports, (f) said tubular extensions being butt Welded to said tubes, and (g) a tubular shell extension on each of said headers surrounding said plurality of tubular extensions and being integrally attached to said tubular shell.

1,361,807 12/20 Bares 1 65-76 2,012,269 11/32 Cornell 165-175 2,391,244 12/45 Jackson 165-158 X 2,919,906 3/56 Haight 165-176 3,048,372 8/62 Newton 165158 FOREIGN PATENTS 1,204,414 3/58 France.

297,509 6/27 Great Britain.

602,601 3/60 Italy.

CHARLES SUKALO, Primary Examiner. 

